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Comment by kdoherty | Hacker News Reader

The phenomenon that is being described where melting ice causes the release of CO2 into the atmosphere seems to have been known to climate scientists, though I don't know whether it has been included in climate change models.

There is a great talk (video online here: https://www.facebook.com/WoodsHoleOcean/videos/1015459031268...) by Richard Alley where exactly this phenomenon is mentioned (see Q&A at ~50:55 in the video, though I highly recommend watching the whole thing).

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The latest IPCC report does not account for Arctic methane release. There were too many variables and they decided to omit it and avoid being alarmist. This is discussed on page 28 of WG1 AR5 SPM (the final 2013 IPCC policy maker report).

But this report is about CO2, not Methane. Methane is yet another reason to be worried.

I believe the article is primarily talking about carbon release as a result of microbial action, I don't think it focuses on a particular form.

The trouser-soiling moment is when the methane clathrate ices start melting.

They call that one the "Clathrate Gun" hypothesis, because you can't un-fire a gun. Once that trigger is pulled, no amount of anthropogenic CO2 emissions reductions will have any effect whatsoever. From then, it will take a positive, intentional, globally coordinated effort to reduce temperatures by other means, or we will be well and truly boned.

We need that global effort to happen yesterday. It's going to be much easier to get the carbon out of the atmosphere by leveraging the already-existing carbon cycle through accelerated silicate weathering than it will be to artificially reduce atmospheric temperatures once huge amounts of methane have been released from sea ice.

Doesn't methane break down in the atmosphere fairly rapidly? From what I'm reading, methane lasts about 12 years while CO2 can stay in the atmosphere for potentially thousands.

Unless we choke to death on methane isn't this less of an issue than CO2 buildup?

Methane is a very potent greenhouse gas, and the release would be absolutely huge. The momentary spike would well cause a lot of CO2 to be released.

On a positive note, while it may not suffice to save human civilization, CO2 likely won't get baked out of rocks. Or at least, it hasn't after previous "methane gun" events.

What has been released after the previous "methane gun" events?

The Paleocene–Eocene Thermal Maximum[0] and the Permian–Triassic extinction[1] may have involved "methane gun" events.

0) http://www.pnas.org/content/113/28/7739.full.pdf

1) http://www.bbc.co.uk/science/horizon/2002/dayearthdied.shtml

"While CO2 persists in the atmosphere for centuries, or even millennia, methane warms the planet on steroids for a decade or two before decaying to CO2.

In those short decades, methane warms the planet by 86 times as much as CO2, according to the Intergovernmental Panel on Climate Change."

Source: https://www.scientificamerican.com/article/how-bad-of-a-gree...

The fear is that the change will be so fast and so drastic that the short lifetime won't save us. It's thought that runaway methane release could result in 6+ degrees (celsius) of warming within just a few decades as massive amounts of methane are released. The influence of methane would end relatively quickly too, but the damage would be incredible.

Nobody is really sure if this would actually happen, though.

Methane does break down much faster than CO2, but over the time scales being discussed here it's MUCH more powerful. From memory so probably somewhat off it's >80x more potent a greenhouse gas over a decade, dropping to only 20x more potent when measured over a century.

The big problem is tipping points. There are a lot of things where an initial big hit can be something you don't recover from, no matter how light the impact might seem when measured over years.

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